This invention relates to patient supports, as may be used, for example, in radiotherapy treatment or diagnostic apparatus.
Various types of patient support are known for use with radiotherapy treatment apparatus, or with X-ray or Magnetic Resonance Imaging systems, and typically comprise a table on which a patient is positioned and a mechanism for adjusting the position of the table. For some applications, it is desired that the patient support table is moveable in the plane of the table so that the patient can be step-wise or continuously driven through an area of the apparatus. This may be desirable for diagnostic, imaging or treatment procedures. Furthermore, it is normally necessary for the table to be situated at approximately 1 m or 120 cm above the ground during the treatment or diagnostic procedure, so that the treatment or imaging head can follow a continuous arc around the patient. This requires the imaging or treatment head to be able to pass beneath the patient support table and thereby imposes a minimum height above the ground for the table. It is known for the height of a patient support table to be adjustable so that loading or unloading of a patient on or from the table can be carried out at a lower position.
Various systems for controllably adjusting the height of the patient support table are known. For example, the patient support may comprise a telescopic pedestal system for height adjustment of the table. Alternatively, a ram may be used for this height adjustment, but this requires a recess in the ground of a depth corresponding to the range of height movement of the patient support table. A further alternative comprises a scissor-jack system which avoids the need for a deep recess in the ground. However, the above systems either require complex and expensive mechanical components or require significant outlay for installation.
U.S. Pat. No. 5,149,074 discloses a patient support table which is vertically displaceable by an arrangement of two arms connected between a base and the support table, the two arms being pivotally connected to each other. To ensure vertical lifting of the patient support, the angles between the lower arm and the base, between the two arms, and between the upper arm and the patient support must each be controlled and synchronised to maintain the patient support in a horizontal plane and to ensure vertical lifting and lowering of the support. This requires numerous control mechanisms to ensure the patient support remains horizontal, and the patient support is constrained to vertical movement only.
According to a first aspect of the present invention there is provided a patient support comprising a base; a first supporting arm pivotally mounted at a first end to the base, the first supporting arm comprising linkages pivotally connected together at four points which define a first parallelogram, a first side of which is fixed relatively to the base in a predetermined orientation, a second opposite side of which, at the second end of the first supporting arm, thereby being constrained to have the same predetermined orientation; a second supporting arm pivotally mounted at a first end to the second end of the first supporting arm, and comprising linkages pivotally connected together at four points which define a second parallelogram, a first side of which, at the first end of the second supporting arm, is fixed to and has the same orientation as the second side of the first parallelogram, a second opposite side of which, at a second end of the second supporting arm, thereby being constrained to have the same orientation; a support member connected to the second end of the second arm; and a patient support table coupled to the support member, means being provided for controlling the pivotal connections between the base and the first supporting arm and between the first supporting arm and the second supporting arm.
In the support according to the first aspect of the invention, the two supporting arms each comprise linkages defining a parallelogram. In this way, it is possible to maintain the support member at a fixed orientation without the need for a specific mechanism to maintain the support member at the desired orientation. The predetermined orientation may be perpendicular to the base, in which case the patient support table may be coupled to the support member so as to be perpendicular to the second side of the second parallelogram, in order that the patient support table is maintained parallel to the base.
The first supporting arm may be mounted to the base through a rotational coupling, enabling rotation about an axis perpendicular to the base. This enables the orientation of the support member within a plane parallel to the base to be adjusted.
The control of the pivotal connection between the base and the first supporting arm may be by means of a driven actuator, and the pivotal connection between the first supporting arm and the second supporting arm may be by a passive arrangement, such that a driven change in the angle between the base and first supporting arm of a first value results in a change in the angle between the first supporting arm and the second supporting arm of twice the first value. Such an arrangement requires only a single driven actuator, and the passive arrangement ensures that the support member is moveable only linearly, and this may be desirable to ensure that there is only vertical movement of the support member. The passive arrangement may comprise meshing gears provided on the first and second supporting arms.
A driven coupling may be provided between the support member and the patient support table, so that the first and second arms enable movement of the support member in a first plane perpendicular to the base (for example vertical) and the driven coupling enables movement of the patient support table in a second plane parallel to the base (for example horizontal). This enables movement of the patient support along three orthogonal axes.
According to a second aspect of the present invention, there is a provided a patient support comprising a base; a first supporting arm pivotally mounted at a first end to the base; a second supporting arm pivotally mounted at a first end to the second end of the first supporting arm; a support member connected to the second end of the second supporting arm; means for maintaining the support member at a constant orientation relatively to the base; a patient support table coupled to the support member by a driven coupling, the first and second arms enabling movement of the support member relatively to the base in a first plane perpendicular to the base, and the driven coupling enabling movement of the patient support table relatively to the support member in a second plane parallel to the base; drive means for controlling the pivotal connection between the base and the first supporting arm and between the first supporting arm and the second supporting arm; and means for controlling the driven coupling.
The driven coupling may comprise third and fourth supporting arms pivotally connected together, or may comprise meshing gears to enable linear movement of the patient support.
The pivotal connection between the base and the first supporting arm, in a patient support according to the first or second aspect of the invention, may be controlled by means of a first driven actuator, and the pivotal connection between the first supporting arm and the second supporting arm may then be controlled by means of a second driven actuator, the actuators being independently controllable.
In this way, the first and second supporting arms enable adjustment of the position of a support member within a plane of movement, not limited to linear movement. For example, the two supporting arms may enable movement of the support member both vertically and horizontally, without the need for any articulated coupling between the support member and the patient support table (although this may be provided for additional freedom of movement).
Thus, in a third aspect of the invention, a patient support comprises; a base; a first supporting arm pivotally mounted at a first end to the base; a second supporting arm pivotally mounted at a first end to the second end of the first supporting arm; a support member connected to the second end of the second supporting arm; means for maintaining the support member at a constant orientation relatively to the base; a patient support table coupled to the support member; and first drive means for controlling the pivotal connection between the base and the first supporting arm and second drive means for controlling the pivotal connection between the first supporting arm and the second supporting arm, the first and second drive means being independently controllable.